Party-line telephone exchange



Nov. 13, 1928.

1,691,080 N. E. NORSTROM PARTY LINE TELEPHONE EXCHANGE Filed June 24, 1926 2 Sheets-Sheet l lac/67%??? Ji s mmfronz/ Nov. 13, 1928.

I N. E. NORSTROM PARTY LINE TELEPHONE EXCHANGE File'd June 24, 1926 2 Sheets-Sheet 2 w r w LEE .\%m

NW 5 NW MM a. NNJ H m .eww 0 NQ m9 Nox' N QHN! III WQN WSW mmw mum WIQNI h%% g @w an 5w gm) Wm .Y b Wm %N\ mamN ww N W k? mm mwml I. W @Hi .5 8% k w WN QWNQKEDI NM NW2 N9 W jzc/erafo r J LA/OTSZII'OWZ/ tions on the line and an Patented Nov. 13, 1928.

UNITED STATES NILsE. NORSTROM, orfenrozicro, ILLINOIS.

PARTY-LINE TELEPHONE EXCHANGE.

Application fi led June 24,

The switching mechanisms at the local sta tions are mechanicallyof a well'lrnown type and dov not need special description. The

' only things about them are the electrical con nections and such mechanical details as will be evidentfrornthe diagrai-i'i' and the'description of the operation;

The apparatus in Fig. 1 is similar to that in Fig. 2', but ornits certain things as. un necessary, v V y In the central office there are a battery and a generator, thepurpose of and connections for which will be evident from the description of the operation. There is also a switching device having two wipers, and a set of contact points for each wiper. The number of contact points in'each set is equal to the number of stations that are or may be on the party line. This switching mechanism is 7 controlled by it keyboard having a series of numbered keys to correspond to the of stations on the line. v There are also certain electrical connectionsoperated byniagnets, a switchboard keya plug and jack, a drop'yand other devices, the character of which will becomeevidentfroin the description to follow.

In the present case the local stations are connected to the central oiliceby one wire and ground. thus obviating theuse of a second wire which is common in party line exchanges. Or the local stations may beconnected to the central office by a metallic cir- V cuit consisting of two wires with no ground connection. Vhile it is not new to'eonnect number a series of local stations to a central Office by one wire and ground OIlly,'StlCh systems have been limited in a number of ways. The purpose of the present systern is to obtain by one 1926. Serial m 118,136;

wire and ground connections allot the a dvantages'which have heretofore been obtained only by the use of two Wires and a ground connection, v v r f r In the present drawirgs I have-illustrated connectlons tor three StZlctIOIlQ'WiHCh are all that are'necessary to explain the system, fIt

is to be understood, however, that the number 00 01? stations on the line are usually more numerous, the apparatus being coinmonly made for twenty stations on a line. To illustrate the operation we will assu1ne thatthe. subscriber at station No. 1 call-scentral and wants to talk with the subscriber at station The subscriber at stationNo. 1 turns the crank of his generator- G, whereupon a cure rent flows. as follows 2T Gr.1 -a3- ground at 15 to 'groundat 16 at station No.

: Whenrin-ging from the generator G, there is a branch from l thru the stepping up magnot H to ground at 16,7 and this causes an operation of the stepping up magnet. However, thisv circuit 'goesrthru 181920, and

the beginning of the inovenient of this n1agr not breaks its own circuit at 19. 'quence is that while-the impulses from the v generator G operate the drop I), they are p v broken up at 19 so that i I .is not operated effectively;

The consethe stepping-magnet ":The impulses over tli'ecirouit lust given 8%.

perate the drop D at the central office,,but' 'aii'ect nothing else. 'lhe operator inserts the plug F in. the adjacent jaclq and presses the switchboard key K to the right to connect her tele Jh'one set; Beginning at the receiver at station No. 1, the talkingcircuit is R---1 3+ 4:5 G-T+QQ Z3 Q4 QS QG QT -telphone se't 2829 30-3'132 1tgro'und at 15 to ground at 16"1718' 19 20 '2i se h ok aesn. i q Upon being-informed that station Noil wants i to talk to station No; 3, theioperatorpresses 5 keysNo 1 find'No, 3 on her'keyboard. These keys are made of insulating material, and

each-one rests on two contact springs which .lo n are 'spread when the corresponding key is depr'essedi. "Adjacent to each key is-a. catch, a" part of one ofwhich issliown'at 35;:idjaeef1t to key No. 2 When a 'ke y isdepressed? its outer sides or the springs which are spread by such-depression. In such depression the key is moved downward so that the ledge 36 on the key passes a short distance below the adjacent catch 35. When the operator re- Y moves her hand the key rises to engagement with the catch. The outer contact springs are so arranged that the one to the left- (above as shown in Fig. 1) is a little nearer to its adjacent contact spring than is the one to the right. When a key is depressed, contact is made to both of the outer springs, but each catch 35 is so related to these springs that when theoperator removes her llZLIlClffIOIIl a depressed key and itrises to its catch, such rise breaks the more distant contact and leaves the other in engagement.

When the operator depresses a key, and before she removes her hand to permit the de pressed key to rise to its catch, a current flows from the battery X thru line 37 and branches 38 and 39 to spring 40 of the highest numbered key on the board. If that key is depressed, as in the present assumption, then the circuitfor this current continues-41- a2- 13 master magnet M- 14t-4c5e6 47-A- 1849-5O51-.

If, however, the highest numbered key on the keyboard is not depressed, then the circuit would be from 10 of the highest numbered key 53 E l -40 or the next key, and so on until it came to a depressed key, after which itwould go thru the corresponding spring 41 of that key to the line 42, and then as before described.

The clrciut ust described permits'the flow of'a current to operate magnets M and A, but

this circuitis immediately broken by the depressed key rising to engagement with its catch 35. However, the operation of the magnet M shifts its adjacent contact springs to hold its own circuit from 385 5 56 l3 and .so on as before. Theoperation of the magnet A moves the holding pawl 5'? into ens 'agement with the ratchet wheel B, and holds 7 this'until the circuit thruM and A is broken will be described hereinafter.

'llhe ratchet wheel B isoperated by a mag net C with its armature 118 and attached pawl. On the. wheel 5' is a wiper 117 which is in electrical connection with the, wheel.

The wheel, wiper' 117 andarinature 118 are all in connection with the base of this switching device so that an electrical connection to fine, and the wiper 117 is so located that it does not reach the first contact point of its series until the wheel has advanced live steps beyond its normal position, which is that shown in the drawing. The insulated wiper 1 18 is so located that it does not reach its first contact point until one step after wiper 11', reaches its first contact point. Also, the contact points are-so spaced that it requires two steps of the wheel'to advance a wiper from one contact point to the next one in the series. Under the arrangement described, when wiper 117 reachesits first contact point, wiper 148 is one step away from its first contact point. At the nextstep, the wiper 1 18 comes to its first contact point and the wiper 11? comes to the space between the first and second contacts. At the next step, wiper 11? comes to its second contact point and wiper 1 18 comes to the spacehetween its first and second contact points. 7

When keys Nos. 1 and 3 are depressed, the first and third contact points for wiper 117 are made alive by connecting them to the battery thru the line 37 and 38, and the springs to the left (above in Fig. 1) of the depressed keys. All other contacts of this series are dead.

f key No. 1 is depressedand no other key,

then the battery X isconnected thru 37-38 39-410 of key, No. 3 5354 1O of key, No. 2 and by a similar loop with 4:0 of key No. 1. As the springs 10 of all keys except'the highest numbered key are connected directly to their respective contacts in the path of wiper 148, and as the highest numbered contact is connected directly with the line 37, it will beevid-ent that pressing key No. 1 makes alive all contacts in the path of wiper 1418.

After the operator has depressed keys Nos. 1 and 3 of the keyboard, she moves key K to the left to shift the adjacent contact springs. A current then flows as follows 2- Iii--37- 59-60--6l'6263tl- 6st--65- 66 6?2 l--23'-2276-5 of all stations on the line ope "sting magnets H to ground at 16 ground 15 at jack 14'." '3l4 3130-68--6970-'Z172- ?3-71-75+ 7677-78-52-X. A branch of this current goes thru 5 and magnets H in Fig. 1".

This current is in the release direction thru the stepping up magnets of the local stations, and thru the corresponding magi'ict in Fig. 1.

Itspurpose is to insure that all switching mechanisms at these places are in their normal positions.

The current ust described also went thru the coil S to operate its armature and shift the adjacent contact springs. lVhen this occurs a current flows X7 9-808182.- S 8384i8586-X. Thercoil S is on thesame core with S and the current thru S serves to hold the adjacent springs in their shifted position when the circuit is broken thru S in subsequent operations,

' ratchet wheel B one step, and operates ma into contact with spring 98. As a when s and s shift their. adjacent contact springs and hold them in that shifted position, a circuit is closed for magnet P as follows X'3787--P S889'90 91929386 Also X79 9 4'- 95-96-C -97 919293'8 X.

This operates the magnet C to advance the f a net P to break its own circult at 88, and the circuit tor the magnet OM94; circuit 1s quickly remade by spr ng 95 coming quence of this, magnet C operates once when magnet P operates, and again when the cir-' cuitfor P is broken In other words, magnet C operates twice for eachoperation of magnet P. A

At the time magnet P operatesto shift the movable springs to the right'it brings spring 73 into connection with contact 58, whereupon a currentflows X57575 8 7372 717069-'683031-32=1t ground at 15 to ground at lfi of alllocahstations on the line stepping'magnets H 5-6 'Z 22'23 24-6766'65+6a S 63 -62- 6l605999100'52X. I There is a branch of this which goes thru the correspond'ing stepping magnet of Fig. 1.

The current flowing thru' the circuit just descrihedis an impulse in the stepping up direction, and acts to advance the switching mechanisms of all stations 0119 5161) At each of the localistations there is a pin 101 inthe path of the driving pawl so that the ratchet wheels'w'ill be advanced only one step for each impulse of this kind; For the corresponding ratchet wl1eel103 of Fig. 1 there is no corresponding stop, with the result that each stepping impulse causes this wheel to move a distance of two or three teeth when the wheels 102 move only one step each. The object of this is simply to causetl'ie wheel 103 to advance further-than the wheels 102 so that when theyjare all released at the same time the wheel 103 will not reac'lritsnormal position until after the other wheels have done so.- It is to he understood that all of the circuit for P.

these wheels have holding pawls whichretain the switching devices in thelr advanced position until rel-eased. These holding pawls and the releasing mechan sms' are not shown as they are well known in the-art andform no part ofthe present invention."

hen P attracts its armature 104E aspring 105 retracts the armaturcgto remake As it is desired that the magnet C should operate twice while the magnet P operates once, the armature 104 is made heavy so that it will not move rapidly. Onthe pivot 106 of the armature 104 is loosely pivoted a weighted arm 107 which is free to vibrate between pins 108 and 109 securedon the armature 104. When the armature is attracted, the pin 108 drives the arm But this last i g and rea si sow'i -1r i h l t it cult is n w ously desciihed the inn 1 0? continues to move forward" until I it engages pin 109. At this ti-methc spring 105 15 beginning to retract armature 104-, and the result of the collision between 31111107 and pin 109 is to retard the retraction oi the armature 104. Asa consequence; the momentum oi" the arm 107 111 passing from p1n-108 to pm 109 is to check-the rate of vibration of the armature, and this is equivalent to add considerable weight to' that armature. In the same way, the passage of thearm 107 from pin 109 to pin 108 on the return stroke checks the rate ofviloration at the other end of the stroke. l c

The armature 104 is retracted by spring 105, and in this movement the arm moves at the speed that the armature 'move's. The back stop for the armature isan electrical contact for completing a circuit for the mg from pin 109 to contact with pin 108 checks this vibration and retains the connection with spring 89 until that "connection is'hroken in the regular order by a 'i'iewoperation of'the magnet P. i

net P, and is placed on a spring 89 so that there w ll be a material period of time dur- "Inc On the ratchet wheel Bis a cam 110 against which rests the spring 76'. When the wheel is advanced, this cam operates to move the spr1ng'76 out o't engagement w th the con tact point 77. This occurs at the first orsecond step of the wheel. l/Vhen the armature j 1047falls back again it closes a circuit in the release direct-ion thru the. stepping mag-nets of the stations before. But this occurs after the wheel B has advanced two steps, and

consequently after the connection-has been broken at 77. T he result is that this release impulse goes from branch 75 thruthe resist? ance 111 to branch 78; This resistancelet-s thru current enough to kill the residual magnetism in the stepping magnets. but not onoughcurrentto release the switches.

At about the third time thefmagnet P; attracts its armature, which would correspond to the fifth forward step'ot the ratchet wheel B, the wiper 117 comes into engagementwith the first contact point- 116 in its-path. As the armature 118 of magnet Cfalls hack, a cir cuit is completed as follows X-3738 112.'of key N0. '1-113 14115 117- base- Before proceeding with a'description of the effect of an impulse over this circuit and thru the magnet E, we will refer to the appa .to the armature 141 is a hooked lever other end of whlchis engaged by pm 1113 on ratus at the local stations. On each wheel 102 isa cam 12-0 w ich corresponds to cam 110 and serves to move the spring 2 from its upper to its lower contact at about the second step of wheel 102. Also on each Wheel 102 is a cam 12 tarranged to engagea spring 130 and push it ou ward into electrical contact with spring 137. At station No. 1 this would occur at the ihird forward step 01" the wheel 10' 102, and would be co-incident with the wiper 117 engaging the first contact 116. At station No. 2 the cam 12% at that station would engage its adjacent spring at the fourth forward step of the corresponding wheel 102, and coincident ith the wiper 1'17 engaging the second contactot its series. No. 3, the corresponding operations would occur at the fifth iorward step, and so on for the other stations on the line.

Returning now to the impulse thru the magnet E, the attraction of its armature shifts the connection from contact 61 to contact 132, whereupon a current i'lQWS as follows alternating generator Q126-12T 128-129-131132G2 66672423-227-6-5 of station N0. l1133 cut-in magnet 13%l--185-136 137 ground at 138 to ground at 1-39- lac-Q. V

This operates tie cut-in magnet 13% so as to attract its polarized armature 141 and shift the adjacent contact springs. V Adjacent the wheel 102. When this wheel at its normal position, this pin or projection 1 13 engages the lever to hold its hook tree from the armature 1 11, but when the wheel advances under the action of its stepping up magnet, the hook 1&2 is in condition to engage and hold armature 1 11 in attracted position soon as its magnet 134.- acts. The purpose here is to hold the adjacent springs in their shifted position.

T he generator operates at about twenty to forty cycles per second. From the circuit last described there is a branch which goes thruthe magnet l, and its armature 127 in the circuit for the cut-in magnet The result oi? this arrangement is that the in 'PlllSBS going from generatortfi are broken up into small fractions, T he inag rnet 1 will operate to move its armature under t impulses because said arms me has no direct rcting spring. "There is a small spaceldl r the hook 14:55 which is carried by the a *mature 1 As a consequence when the hook 1415 st :cs the swing 10 1 to shift the electrical connections, the momentum of moving parts. suliicient to make the shift and have the a ture caught by hock lit-2n 1n the circuit from the gcneratorh}. t ere is a branch from line thru the stepping up magnets. but the armatures of these magnets are held in central position by compara- Avg,

At station 7 wiper let-8 to its first contact point, and the wiper 117 to the vacant space between its first and second contact points. it key No. .1 was the onl one depressed. then a-circuitwill be p formed as follows X37-88-30 l0 the highest numbered key on the board which in this case is key No. 3 -53h i-10 of key No. 2 similar loop to 40 oi key No. 1 1-l-.6-147-1l81-l0--. magnet N 52 X. if key No. 2 was depressed, then the circuit would be broken 10 of key No. 2 and there would be no ilse thru magnet N. A circuit would, however, he established when wiper 14-8 reached theseccnd contact by wire 150 from {10 of key No. 2. In the present case we have key No. 3 depressed and the circuit broken at 10 of key No. 3 for all con tacts of lowernumbers in the path or". wiper lhe last. contact of this series'is connected directly to battery X by branch 151 from line 37, and magnet N will he operated when the wiper 148 reaches this-contact."

When wiper 11? comes to a contact point, it does nothing immediately or directly, but it the correspondingly numbered key is depressed, then a circuit is completed for magnet E when the armature 118 falls back. The operation of E throws impulses onto the line, and these impulses go thru the cutin coil of the correspondingly numbcrec station. On the assumption that keys Nos. 1 and 3 are depressed then when wiper 11'? to its first contact point the battery X will be connected to wiper 117 thru spring lll of key No. 1, and when the armature. 118 falls back this connection will be extended thru the magnet E to the other pole of the battery. This will'put impulses from Q; thru cut-in coil 13 1 at station No; 1 because at that station cam 124- has the contact springs 136137 closed. When wiper 11? comes to its secont contact point, nothing of this kind Jill occur because key No. 2 is not depressed and its springcorresponding to spring 11 1 of key No. 1 will be open. Butwhen wiper 11? comes to its third contact point, the previous active conditions will be repeated because key No. 3 is depressed and because the springs 130-137 are ClOII d at this time at the third station.

In the previous description it was pointed out that when wiper 14S comes to the contact point-of its series which corresponds to the highest numbered key depressed, there is a circuit completed thru the magnet N. The resultant actuation of this magnet breaks the circuit for the magnets M and A at the point 10. 7

Breaking the circuit thru the magnet M permits the adjacent contact springs to return to'normalposition, and as the other lflH.

magnets are controlled thru these springs in their shifted position, the parts controlled by those other magnets also-return to normal position as is common in exchanges of this character. And breaking the circuit thru magnet A releases the holding pawl from wheel B and permits that wheel to reti'irn to normal position. By suitable connections,

the returnv of the various -parts to normal position releases catches so that the depressed keys on the keyboard may rise to their normal positions. These connections arenot shown because there is nothing new or novel aboutthem, and because they form no part of the present invention. v I

During these operations the operator is holding her key K to the left, and as soon as the parts controlled by magnet M have re- WVhen thesubscribers have removed their receivers, the talking circuitis R at station No. 1- 1-2159.160161, 162168 164:--15313345-6 to station No. 3

.54133153164-16 162161 16O 159 2 1R 34158-+3321-20 19181.7 ground at 1 6 to station No. 1- 1718192021-33 15834 R.

lVhen the subscribers are thru talking they turn their generator cranks, or at least one of them does, and a current flows-as follows G-1-2159160 1G1-162163%+164 l531834l56+7222 2425- clearing out drop 165-29'30313Q+ 14 ground at 15 and back to ground at 16 at local station 1718-192 021 G. The

operator thereupon removes the plugto disconnect the line. Y

In describing the first stepping up impulse is a contact spring 167 which is pushed into engagement with a contact 166 whenever these magnets are operated in the stepping direction. At the time the first stepping'up' impulse flows as described,-this electricalconnection is made and a current flows:- X-87- to Fig. 1 166167168169- 170171172 magnet l73 174 175 1761778586X.

caught and held by the catch 17 9 which was released by the first forward step of wheel 103. At the time the operator removes the plug as before stated,an impulse flows as follows X37 to Fig. 1 +lZ8 179. 9.8 76 5 -and 5 of all stations on theline to ground 1 5-at the 181175.l76-1778 5 86-X.

This is an impulse in the release direction thru all of the switching mechanisms, and is held until the wheel 103 of Fig. 1 reaches its normal position and releases'catch' 179 from t armature 178. As previously stated, Wheel 103 advances furtherthan'do Wheels 102, and

the result is that this current in the release direction isnot brokenuntil after the switchinginechan'isms at the local stationshave hadample timeto' reach normal position; But

when wheel 103 does reach its normal posi t-ion, all parts are automatically returned to normal position. I

Reviewing the operations very brietly,the,

subscriber calls central in anordinary manner and tells'the operator the station with which he Wishes to talk. Upon receiving the desired information, the operator presses the keys on the keyboard'which represent the calling andthe to-be called stations, and immediately thereafter moves her switchboard key K to the left. :The actof depressing-- the keyboard keys starts a series of automatic electricaloperations within the .central-oflice which prepares the apl' aratus therein for sending impulses o-ver the'line'to select thedesired stations and connect them telephonically to thel'ine, and at the sametimeito look i out all unselected stations. The act of press ingthe switchboard key results ii -starting the prepared apparatus into automatic operation .to select and signal'the desired stations andthen to return itself to'its normal position as it existed before the depression of the keyboard keys. 7 Reviewing some parts again, but notqu'ite so hriefly,the operator depresses a key repres e nting -the desired station. Th Operation breaks one electrical connection and makes? two others, one'of which is ten'iporary and thru the station devices it was stated that a branch went thru 5 and the stepping up mag nets of Fig. 13 Adjacent to. these-magnets number thanv the one depressed. The tem-.

porary connection sends animpulse tooperate a' master magnet M a'nd to shift a series of electricalconnections, and tooperate a magnet A to put a holding pawl in contact with a master switch B. The connections shift-edproduce a holding circuit for magnets Mend A[ The connection which is held is. I one lead-ing from the'battery to a corr'clspon'd- This operates to shift the contact springs adjacent to the magnet 173, and' this shifted positionis held by the armature"l78being ing contact-point on the master switch'inthe path of wiper 117 w described, operator shifts the switchboard key to the left to send a release impulse from the battery thru all of the stations on the line and thru coil S to shift adjacent springs. This last makes a holding circuit thru the coil S which is independent of the impulses thru the stations;

The springs shifted by magnets S S close a circuit for the magnet P, which is the motive part of an impulse sender, and for the magnet C to operate the master switch. This impulse sender is in the form of a slow speed vibrator, and might properly be called a pole changer because the impulses sentare alternately in the opposite direction. The operations of the magnet P close connections for tl e magnet G at the terminal of each vibration of the parts vibrated so that the magnet G operates at twice the frequency of mag net P. a

At each attraction of its armature by the magnet P an impulse in the stepping up direction flows thru all stations on theline, an l at each retraction an impulse in the release direction flows thru all stations. But the first forward movement of the master switch inserts resistance in the branch for these release'impulses so that they are ineffective to produce actual release.

. When the wiper 11': reaches a contact corresponding to a depressed key, battery connections are extended to that wiper, and

1 when armature 118 falls back an impulse goes thru magnet E. The operation of E shifts the party line fromv the battery to the generator Q, so that broken up impulses flow thru the cut-in magnet of the station which corresponds to the key depressed on the keyboard.

The effect just described will be repeated each time vthe wiper 1 17 comes tea contact corresponding to a depressed key. Wiper 1&8 is one step behind wiper 117, and when wiper 1&8 comes to its contact which represents the highest numbered key depressed, a current flows thru the magnet N to cause a restoration of all of the central oflice apparatus to its normal position. During these operations the operator is iolding her switchboard key K to the left, and when these parts return to normal position ringing impulses flow from generator Q over the'line and thru the bells of selected stations.

The pole changer which serves as an impulse sender is one which works automatically when started into operation, and which automatically comes to a stop at a definite position as soon as it has sent the number ofv impulses previously indicated by the manual operation of the keyboard. This automatic stoppage saves wear and tear of parts which occur inpole changers which operate continuously. The fact that the-pole changer always stops in a definite position insures that it will be in proper position to send a release impulse thru the stations when the operator removes the plug to disconnect the sponse to a call from some subscriber on the line, such insertion breaks the circuit for the drop D at the spring 14. When the first stepping up impulse flows, the branch thru the magnet H closes another branch thru the magnet 173 of Fig. 1 and this magnet breaks the circuit for the drop at another place so that, on removing the plug to disconnect the line the resultant release impulse will not fl w thru the low wound drop. This is impertant because the party line may be twenty miles long or more, and if the drop was in parallel with the stations, not enough current would go thru to'release the stations.

At the local stations, there is a sub-branch at which leads to the cutin coils 13 1. In this sub-branch is a condenser 200 to prevent the battery impulses for magnets H from also operating the cut-in coils Each time astepping impulse flows over the line it gives each condenser 200 a charge, and when the impulse ceases, the condenser is discharged and causesa light impulse to flow thru the associated magnet 134.

As the armature l il of this magnet is polarized and has no retracting spring, the impulse of discharge is sufficient to move the armature on its pivot. The polarization of this armature is so related to the direction of impulse due to dischargethat the endwhich carries the hook 145 is moved away from the pol-e of the magnet.

As previously described, the alternating genator Q, runs at comparatively slow speed, and the magnet I operates at high speed. The result of this arrangement is that the impulses which go from generator (.15 over the line are really each a series of very short impulses in one direction followed by a series of equally short impulses in the opposite direction. Vhen the magnet E is operated to shift the line from the battery to the generator Q, the first broken up impulses from the generator find the armature 141 prepared by being tilted on its pivot away from the position to which it is to be moved by those impulses. If the first broken up impulses are of the same direction as the discharge from the condenser, then they are without effect. But when the impulses are in the opposite direction, they operate to move the armature thru a considerable distance before the resistance of contact spring 164 is encountered, and during that non-resisted movement the armature acquires momentum which enables it toovercome the resistance of the spring and permit the armature to be caught and held by the hook 142.

The circuits atthe local stations are so arfrom each branch 5 Lil . I "1,691,080 I Y W 7 i the shunt for the generator is the same.

At each local station is a spring supported at 20% and having a weight 21 1 on its free end.

I Nearby is a frame 205 which carries a springsupported pin 206 having a button 207 which may be reached by the subscriber. These parts are so arranged that if the button 20 is depressed quickly, the pin 206 will strike. the spring 203 and the momentum given to the weightby suchquick stroke will carryspring 203 far enough down to strike spring 161 and break its contact with spring 162.

I But the parts are also so arranged that holding the button 207 depressed does not hold spring 161 from spring 162 because the pin 206 is too short to maintain-this condition. The connection between 161 andl62 is in the shunt previously described, Depressing the button 207 slowly will not affect this'connection, but depressing it quickly gives the weight a momentum which will result in a very brief opening ofthe connection between 161 and 162. I

If a subscriberwhois lockedout turns his generator G, and while turning it gives his button a series of taps, the generator shunt will be broken at intervals, andateach break current will flow as follows G'12 local station1718-192021G.

This would operate the drop which is ordinarily used to indicate that a conversation is finished. In ringing off, the operation of the drop 165 is accompanied by a buzzing sound plainly audible to the operator, but the operation of the drop by an emergency signal of this kind would be by single ticks separated by intervals. I the two is readily observable by the operator who would know that a signal of this kind was an emergency call from some locked out subscriber. Upon receiving such signal she would proceed in the ordinary manner to answer the emergency call.

The party line consists of two line limbs which connect a central ofiice and a series of local stations together.

connection as circumstances may dictate. These two line limbs constitute a path over 'which electrical impulses flow in different The distinction, between.

One limb is a wire, and the other limb is either a wlre or ground.

local station to the central oilice,--ta lkin gfbetween subscriber and operator, 'initia'l release impulse to insure that all local station devices 1 are at'their normal positions, stepping impulses go ng thru all stations, cut-in impulses thru' selected stations, call signals to subscribers, talking between subscribers, emergency signals, and ringing off. The apparatus and operations described are for producing these results in an efficient manner when that single path is the onlymeans of.

intercoinmunication.

- VVhatI claim is: Y

1. A slow speed pole changer, a inaster switch having wipers insulated from each 'other and a series of contact points in the path of each wiper, andmeansincluding a battery and connections so arranged that the mast-er switch will make oneforward step at each alternation of the pole changer,

2. A slow speed pole changer, a master switch having wipers insulated from each other, a series of contact points in the path of each wiper, said wipers andcontact points being so arranged that the wipers will come to their respective contact points at alternate forward steps of the master switch, and means including a battery and connections so arranged that the masterswitch will make one forwardstep at each alternation ofthe pole changer.- 1 3. In a telephone exchange having aseries of local stations on a party line, a master switch having two sets of contact points each set of which has as many contactpoints in it as there are stations on the party line, a wiper on the switch for each set of contact points, I

said wipers being so arranged that they come to their contactpoints at alternate forward I steps of the switch, and an impulse sender controlling the operations of the switch and itself operating at one half of the frequency of the switch.

4. In atelephone exchange having aseries of stations on a party line, a master switch having two setsef contact points each corresponding to the stations on th-eline and also having a wiper for each'set of contact points, a keyboard havingkeys corresponding to the stations, an impulse sender arranged to send impulses over the line to the stations and also to operate the master sw tch,

means'by which depressed. keys on the key board control part of the operations of the I master switch, and means bywhich the master switch controls part of the impulses sent by the impulse sender.

5. In a telephone exchange having a series of stations on a party line, a master switch having two sets of'contact points corresponding to the stations on the line and a wiper for each set of contact points,'sai d wipers being insulated from each other so arranged that they come to their contact porn-ts at alternate forward stepsof the switch,-means for movthe line to operate ing the switch step by step, means for sending electrical impulses over the line to select desired stations and connect them telephonically to the line, and means for controlling such impulses thru the wipers of said switch.

6. A party line having local stat-ions thereon, two magnets at each station by the operation of which desired stations are connected telephonically to the line and other stations are excluded from such connection, two sources of electricity located at the central of lice, manually operated means forconn-ecting the line to the'central oilice, uton atically operating means by which impulses flow over simultaneously corresponding magnets at all of til; stations, and addi tional automatically operating means by which impulses from the second source will iiow over the same path between stations to operate the s cond magnet at some previously determined station.

7 A party line having a series of local sta' tions connected to a central otiice by a single electrical patlntwo magnets at each station, one oi the magnets at each station being re sponsive in opposite ways to impulses of a given character but in opposite directions and the other magnet being responsive to impulses of diil'erent character, two sources of electricity at the central otlice each of which is adapted to furnish impulses suitable for the operation of one lrind of said magnets,

and automatically operating means for causing impulses to flow from both sources over the sine path to connect desired stations telephonically to the path over which the impulses flow.

8. A local station connected to a party line, two magnets in the station and connected in parallel between the limbs of the -line, means for sending direct and alternating impulses at dill rent' times over the line, and a condenser in the branch for one of said magnets, said condenser serving to prevent direct impulses from operating said magnet and by its discharge between impulsw serving to prepare said magnet for subsequent operation by alternating impulses.

9. The combination with a central oiiice, a party line having local'stations thereon, and apparatus at the local stations operated by impulses flowing over the party line, of a battery, an impulsesender automatically operated from said battery, and means by which upon the impulse sender being started into operation it will send a predetermined number o1 impulses over the party line and will automatically come to rest at the position from which it was started. 7

10. A pole changer, a battery "from which the pole changeris automatically operated and from which it sends impulses alternately in opposite directions over a line, and means including manually operated keys and connections controlled thereby by which upon the pole changer being started into operation it will send any predetermined number of impulses over the line and then automatically come to rest at the position from which it started. 7 i

11. A party line having a central oliice and any desired nun'iber of local stations thereon, apparatusoperatedby selecting and connecting magnets at each station, both of which magnets are operated over the same path between stations and oil-ice, a source of electrical impulses for the selecting magi zts and another source of in'ipulses for the connecting magnets, means for automatically shifting the line from one source to the other 111d be :l: again, and means to returniug g' the operated apparatus from any degree of advance by an impulse sent over the same path used for 0Q- lecting and connecting impulses.

12. A party line having a central ofiicc and a series of l cal stations thereon, selecting and connecting magnets at each station, both of which magnets are operated over the same path between stations and otiice, automatically operating means for sending impulses from the oliice for operating all of the select- .ing magnets and predetermined ones of the connecting magnets, and automatically operating means for arresting the impulse sending operations as soon as the predetermined connecting magnets have been operated.

13. A party line having a series of local stations thereon, a central oi'iice provided with a source of electricity to operate and release devices at the local stations by impulses sent over the party line, a signaling device by which a subscriber at a local station calls the operator at the central ol 'ce, a plug and jack for connecting the line to the o'llice apparatus and for breaking the circuit for the signaling device g operating impul as over the line after the plug is inserted and a release impulse when the plug is removed, and means operated by the first operr ing impu e to breal: the circuit of the s lin do so at another place so the release mipuise'will not llow thru-thc signaling device.

14-. A. central oliice and a series of local stations connected to the oliice by a party line, means for sending impulses over the line to connect selected stations telcphonically to the line and to exclude non-selec ed ones by shunting the receivers and signaling generators thereat, and an emergency button located at each station by the pressing of which the subscriber thcreat may break the shunt "tor his generator for an automatically limited period to permit a signaling impulse to how from the generator to the cities.

15. A central office and a series of local stations connected to the ofiice by party line, means for connecting selected stations telephonically to the line and for excluding other stations -from all electrical connection with by such insertion, means for sendin the line, and an emergency device at each local station by the operation of which a subscriber at an excluded station may obtain electrical connection With the line for an autoniatically limited period to signal the central line and unselected stations are excluded by 10 having their recelvers and signaling generators shunted Within their stations, an

emergency button at each station, and a Weight movable from normal po'sltion by a sudden depression ofsaid button, the momentum of the Weightserving tomake a ver brief break inthe shunt Which will let thru a very brief signal from the generator, but,

will not otherwise affect said shunt.

NILS NORSTROM. 

